Interpretation of the N1sphotoelectron spectra of chemisorbedN2in terms of local molecule-metal interactions

Results of ab initio generalized valence bond configuration interaction calculations on the N 1s photoelectron spectrum of a linear ${\mathrm{NiN}}_2$ cluster with the geometry optimized for the neutral ground state are reported. The energy difference between the two inequivalent nitrogen-core ionizations is determined to vary between ∼1.2 and ∼0.9 eV depending on the Ni-${\mathrm{N}}_2$ internuclear distance and bond energy. We compare the calculated electron-binding-energy difference of the two N 1s ionizations with recent experimental results and show that the observed spectral function is determined primarily by the local bonding properties of the complex, i.e., by the inequivalency of the N 1s core holes.